The present invention relates to a circuit arrangement with a base body. One or more substrates are provided on the top surface of the base body with a positive-pole conductive strip, a negative-pole conductive strip, and an AC conductive strip as well as auxiliary connections, with components such as transistors, thyristors, diodes, resistors, integrated circuits or sensors, at least some of which are in contact with said conductive strips, with an intermediate-circuit board with a positive-pole DC connection and a negative-pole DC connection, and with one or more electrical capacitors connected between the positive-pole DC connection and the negative-pole DC connection, and with one or more AC connectors.
A circuit arrangement with low parasitic inductances, with an electrically insulating substrate on which mutually electrically insulated metallic conductive strips carrying power switches is disclosed in the earlier patent application 100 37 533.2. In that reference, the power switches include power transistors formed preferably from MOSFETs or IGBTs.
The operation of such a circuit arrangement generates heat in the intermediate circuit, on the substrate and on the AC connection elements. In the prior art, the intermediate circuit is cooled through convection at the components. The heat of the substrate is dissipated through direct contact with a cooling body. The heat of the AC connection elements is also dissipated only through convection. The heat of the AC connection elements increases their ohmic resistance and thus reduces their current-load capacity. Furthermore, the one or more AC connection elements may include other components, such as sensors, whose function is impaired by the heat.
It is the object of the present invention to create a circuit arrangement of the kind named above, with low parasitic inductance, where the complexity of manufacturing and assembly is low, which provides excellent vibration and shock resistance and facilitates the improved dissipation of heat generated in the intermediate circuit and/or the connection elements to a cooling body.
These objects are achieved with a circuit arrangement of the kind named above according to the invention, with one or more of the following arrangements:
The intermediate-circuit board includes contacts for making a low-inductance contact with the positive-pole conductive strip and the negative-pole conductive strip of one or more substrates, whereby a corresponding AC connection element with contacts is assigned to the intermediate-circuit board and the one or more substrates, and a compression device is provided for the electrical connection of the contacts of the intermediate-circuit board and the one or more AC connection elements with the corresponding conductive strips of the one or more substrates.
One or more connection pins for external electrical connection are brought into thermal contact with the cooling body by means of an electrically insulating and thermally conducting body.
The internal connecting tabs of the one or more current connections include sections by which these connecting tabs form a connection with the cooling body via a thermally conducting and electrically insulating body.
The intermediate-circuit board with the one or more capacitors to be cooled includes contacts for the direct connection with the positive-pole conductive strips and the negative-pole conductive strip of the one or more substrates.
The circuit arrangement according to the invention preferably includes three substrates for the three AC phases (U, V, W). Such a circuit arrangement has three AC connections.
Since the circuit arrangement according to the invention is usually a performance class circuit arrangement, it is preferred that the base body is mounted on a cooling body, with the underside of the one or more substrates in thermally conducting contact with the cooling body. For that purpose, the underside of the one or more substrates can have a metal coating by which a large area of the substrate lies on the base body or cooling body. The base body is in the shape of a frame and includes one or more compartments for a corresponding substrate.
A relatively simple circuit arrangement that can be produced at low manufacturing cost results when in accordance with the invention, the intermediate-circuit board has a first metal surface element with the positive-pole DC connection and a second metal surface element with the negative-pole DC connection. The positive-pole and negative-pole DC connections are electrically insulated from each other, whereby the connection elements of the one or more capacitors of the intermediate-circuit board are in contact with the corresponding metal surface element, and the contacts of the intermediate-circuit board are formed in one piece with the corresponding metal surface element of the one or more substrates. Advantageously, the metal surface elements for the positive-pole DC connection and the negative-pole DC connection can be made of a stamped and appropriately bent sheet metal such as copper. This results in a circuit arrangement with an intermediate-circuit board which can be produced simply and cost-effectively, whereby in addition to those advantages, the design is also compact, mechanically robust and of low inductance.
The electrical insulation of the metal surface element of the positive-pole DC connection and the negative-pole DC connection can be accomplished by a simple flat element made of electrically insulating material. For the external electrical connection of the DC and AC connections, connector pins are provided in the base body and holes in the corresponding connection elements.
Another possibility is, for example, to provide an insulating intermediate-circuit board whose one main surface has a metal coating connected to the positive-pole DC connection and whose opposite second main surface has a metal coating connected to the negative-pole DC connection. The contacts of the intermediate-circuit board have contact fingers for properly contacting the intermediate-circuit board.
Correspondingly, the one or more AC connections can have contacts which also have contact fingers for properly contacting the contacts of the one or more AC connection elements. However, such a plug-in contact requires a fairly substantial installation effort. For that reason it is preferable to design the contacts of the two DC connections of the intermediate-circuit board in one piece with the corresponding metal surface elements, and also to design the contacts of the one or more AC connection elements in one piece with same.
In the circuit arrangement according to the invention, it has been proven advantageous to make the electrical contact of the connection elements of the intermediate-circuit board and the one or more AC connection element with the corresponding conductive strips of the one or more substrates established by means of a compression device. The compression device includes a rigid compression body and a compression element of limited flexibility whose surface dimensions are adapted to the compression body. It is practical to place between the rigid compression body, which is preferably made of metal, and the compression element of limited flexibility, an intermediate body of electrically insulating material which has pipe-like through-elements extending through the rigid compression body. A driver circuit can be arranged on the compression device of the circuit arrangement according to the invention, whereby contact wires, extending through the compression device, are pressure-contacted with the corresponding conductive strips and auxiliary connections of the one or more substrates.
The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements.